Question

water striders kill and consume their prey (other insects) by
trapping air in the hair on its legs so it doesnt get wet
ripping it apart and eating it
injecting digestive enzymes into an insects weak spot and sucking up its juices
asking the other insect nicely for permission to eat it
overpowering the other insect, then drowning it

Explanation:

Water striders are predatory insects. They use their sharp mouth - parts to inject digestive enzymes into an insect's weak spot and then suck up the liquefied internal juices. Trapping air in leg - hair is for water - walking, not predation. Ripping apart, asking for permission, and drowning are not their predation methods.

Answer:

injecting digestive enzymes into an insect's weak spot and sucking up its juices